During the lifespan of an ink jet printhead assemblies or "pens", air or gas bubbles develop in the ink and coalesce into larger bubbles. As the bubbles form and coalesce, they tend to accumulate in the ink feed port, filter areas and ink feed channels of the pen. If the amount of air or gas bubbles increases significantly, performance of the pen may be affected. For disposable pens, air accumulation is not typically a significant problem. However, for longer life permanent or semi-permanent pens, and for high quality, high speed pens, substantial air or gas bubble accumulation may adversely affect printhead performance by causing misfiring or ink flow blockages.
A primary source causing air or gas bubbles in the ink feed port, between the printhead and ink cartridge, arises from the removal and connection of ink cartridges with the pen. If a spent ink cartridge is allowed to run dry of ink, air will fill the ink feed port connecting the cartridge to the carrier/printhead assembly. Even if the ink cartridge is not run dry of ink, a certain amount of air is introduced into the ink feed port each time the ink cartridge is connected and/or disconnected from the carrier/printhead assembly. Some of the air or gas bubbles which make their way into the ink flow channels of the pen are removed from the printhead through ejection orifices, however, a portion of the air or gas bubbles under the action of buoyancy may migrate back through the ink feed paths into the ink feed port in the connection between the pen and the ink cartridge.
Priming the pen by ejection of ink may remove air or gas bubbles from the printhead itself, however, there may still be a substantial amount of air in the ink feed port due to cartridge replacement. This air is effectively trapped between the pen and the ink cartridge in the connection port connecting the cartridge to the pen assembly.
An object of the invention is to provide an apparatus and method for removing air and gas bubbles from an ink jet pen.
Another object of the invention is to provide a device for removing a substantial quantity of air from an ink feed port.
Still another object of the invention is to improve the operation of a permanent or semi-permanent pen.